Earth is approximately 1.5 ? 108 km from the sun. How many minutes does it take light to travel from the sun to Earth? The speed of light is 3.0 ? 108 m/s.

Question

Very hard for me.... This is a question from my honors chemistry homework

Answer 1

The conversion of units is very important in this problem.

 

"How many minutes?"  means  (distance in m) / (speed in m/s)  

    [when invert and multiply, m cancels out giving seconds, which must be converted to minutes]

 

   1.5 * 10⁸ km * (1000 m / km) / ( 3.0*10⁸ m/sec)

   1.5 + 1000 m / (3.0 m/sec)

    500 sec * (1 min / 60 sec)

       8 min 20 sec

 

So, when you 'see' the sun, that is where it was approximately 8 1/3 minutes ago.